A considerable discussion of the matter of human comfort as affected by the conditions of the environment is set forth in our U.S. Pat. No. 4,504,157, issued on Mar. 12, 1985. Described therein is a composite sensor, and a circuit for the same, that takes into account real temperature, wind velocity, moisture content (humidity), and solar effects in the determination of chill temperature or chill factor. This can be generally referred to as a "comfort index". The content of that patent is incorporated herein by reference. Basically, the principle of that composite sensor is the determination of the amount of power that is required to maintain a given temperature (or temperature differential) within the sensor as that temperature, or temperature differential, is affected by the environmental variables. An output signal, in the form of a voltage, is related to the chill temperature produced by those variables.
In order to obtain the output voltage from the circuit shown in the patent, a signal related to the square root of the power is squared within a "power meter" circuit. Although this manner of obtaining the output signal is generally satisfactory, some drift has been observed in long-term operations of the circuit.
It is recognized that there are applications for a chill temperature system wherein special "weighting" of the influence of one or more of the four variables may be desirable either over a wide or narrow range of the chill temperature value. For example, it may be desirable to select a response that is particularly affected by humidity, temperature, wind velocity or solar effects. This special response might be desired, for example, to produce a readout of the chill temperature having a relationship that more closely follows the relationships that have been established by prior art instruments or by human response. Also, for certain research studies, it may be desirable to give greater weight to one of these effects than can be achieved through the use of the composite sensor alone.
Accordingly, it is a primary object of the present invention to provide a chill temperature meter that provides an output that is more truly a measure of the comfort index than has been possible using devices of the prior art.
It is another object of the present invention to provide a chill temperature meter that automatically samples and averages the output signal from a composite sensor and discriminates against those sample signals that appear to deviate in an amount greater than a selected value from the average in order to eliminate possibly spurious information.
It is a further object of the present invention to provide a chill temperature meter system wherein the contribution of one or more of the major variables affecting the index can be weighted in selected regions of response to give a selected control of the output information.
These and other objects of the present invention will become apparent upon a consideration of the description given hereinafter as referenced to the drawing.